fix(billing): surface quota saturation events for admin auditing

Thread int32 saturation clamps from tiered settlement and video task
recompute into the consume/task logs under admin_info, so oversized or
malformed billing inputs stay auditable. Clamp negative audio duration
before token conversion and gate the saturation UI markers on admin.

service/tiered_settle.go

@@ -112,5 +112,10 @@ func TryTieredSettle(relayInfo *relaycommon.RelayInfo, params billingexpr.TokenP
 		return true, quota, nil
 	}
 
+	// Surface any int32 saturation from settlement onto RelayInfo so the
+	// consume log records it under admin_info, regardless of which caller
+	// (text, audio, WSS) consumes the returned quota. First non-nil wins.
+	noteQuotaClamp(relayInfo, tr.Clamp)
+
 	return true, tr.ActualQuotaAfterGroup, &tr
 }